[filesystem] avoid zero-skip loop in HadoopDataInputStream

[wolfkill]

Fixes #3718.

Root Cause

HadoopDataInputStream.seek() optimizes small forward seeks by skipping instead of issuing a Hadoop seek().

The old local skipFully() loop assumed every FSDataInputStream.skip(bytes) call makes forward progress. Some streams return 0 at EOF or when no bytes can currently be skipped. In that case the remaining byte count never decreases and the loop can spin forever.

Changes

• Delegate small forward skips to Hadoop's org.apache.hadoop.io.IOUtils.skipFully(InputStream, long).
• Remove the local skipFully implementation.
• Add a regression test using a seekable stream that returns one zero-byte skip and then EOF on read, verifying EOFException and that zero-progress skip is not retried.

Validation

• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -Dtest=HadoopDataInputStreamTest#testSeekPastEndOfStreamThrowsEOFException -DfailIfNoTests=false test
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -Dtest=HadoopDataInputStreamTest -DfailIfNoTests=false test
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -DfailIfNoTests=false test
• git diff --check upstream/main...HEAD

[litiliu]

would it be better to use the org.apache.hadoop.io.IOUtils.skipFully?

[wolfkill]

Updated this to use org.apache.hadoop.io.IOUtils.skipFully(fsDataInputStream, delta).

I checked the Hadoop 3.4.0 implementation before changing it: when skip() returns 0, IOUtils.skipFully attempts a single-byte read() and throws EOFException if that returns -1, so it avoids the zero-skip loop and gives the expected prompt EOF signal for seek-past-end.

The regression test now verifies that path by asserting EOFException, one skip() call, and one EOF read() call. I also rebased the branch onto latest apache/main; current branch head is e324d87e, and compare reports behind_by=0, ahead_by=1.

Local verification:

• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -Dtest=HadoopDataInputStreamTest#testSeekPastEndOfStreamThrowsEOFException -DfailIfNoTests=false test
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -Dtest=HadoopDataInputStreamTest -DfailIfNoTests=false test
• JAVA_HOME=/Users/cc/Library/Java/JavaVirtualMachines/corretto-18.0.2/Contents/Home mvn -pl fluss-filesystems/fluss-fs-hadoop -am -DfailIfNoTests=false test
• git diff --check upstream/main...HEAD

[litiliu]

looks good to me